Method And Device For Aiding The Evaluation Of A Flight Trajectory Intended To Be Followed By An Aircraft In A Constrained Environment

ABSTRACT

Method and device for aiding the evaluation of a flight trajectory intended to be followed by an aircraft in a constrained environment. 
     The device includes for determining and displaying a zone (ZL) which is free of obstacles (O 1,  O 2 ), around a flight trajectory (TV), this free zone (ZL) illustrating the possible maneuver margin of the aircraft along the whole flight trajectory (TV).

The present invention relates to a method and a device for aiding the evaluation of a flight trajectory intended to the followed by an aircraft, in particular a transport airplane, in a constrained environment.

Within the context of the present invention, a constrained environment means an environment (or zone of the space with a given shape and size) being defined around the position of the aircraft and being able to contain objects (or obstacles), with which the aircraft should avoid getting into collision, including for obvious safety reasons or merely for flight comfort reasons, these objects being either stationary objects such as mountains or hills or mobile (or dynamic) objects such as meteorological disturbance zones, including stormy zones or other aircrafts.

The present invention applies to any type of flight trajectory being intended to be followed by an aircraft. It could be, in particular, a flight trajectory transmitted by the flight management system of the aircraft or by another usual system able to provide a prediction of the geometry of the future trajectory. It could also be a deposited flight plane or a trajectory generated during the flight phase.

The present invention aims at giving the pilots of the aircraft the possibility to evaluate the validity of the flight trajectory being considered in a dynamic environment (with a stormy zone or other airplanes progressing in the same space for instance) with the object, including, to support the crew in making on board a decision in such a constrained environment.

Nowadays, there is no tool for supporting or aiding the evaluation of a trajectory in aircraft cockpits. In particular, a usual navigation display of the ND (<<Navigation Display>>) type displays the current flight plane, but does not supply any information regarding, for instance, margins associated with this flight plane.

The present invention aims at remedying these drawbacks. It relates to a method for aiding the crew of an aircraft, in particular of a transport airplane, to evaluate any flight trajectory being intended to be followed by this aircraft in a constrained environment, that is in an environment able to contain stationary and mobile obstacles.

According to this invention, said device is remarkable in that:

A/ at least one first database containing mobile obstacles and at least one second database containing stationary obstacles are taken into consideration, relative at least to the environment of the aircraft, a plurality of successive points is automatically determined of said flight trajectory, referred to as trial points, and the following operations are automatically implemented, and this individually for each one of said successive trial points of said flight trajectory:

a) the passage time of the aircraft is estimated at the trial point being considered;

b) the positions of the mobile obstacles are extrapolated at said passage time, by means of said first database; and

c) a collision trial is implemented for checking whether a trial vector, being provided perpendicularly to a shifting vector of the aircraft at said trial point, intercepts, on the one hand mobile obstacles at extrapolated positions at said passage time, and on the other hand stationary obstacles of said second data base, and critical points are determined on opposite sides of the trial point being considered, depending on the result of said collision trial;

B/ the thus determined critical points are automatically linked together so as to form a zone, referred to as a free zone, around said flight trajectory; and

C/ said flight trajectory is automatically presented on a display of the aircraft, as well as, associated with this flight trajectory, said free zone allowing to aid to evaluate the flight trajectory.

Thus, thanks to the present invention, a display is provided emphasizing a zone being free of any obstacle around a flight trajectory being defined in a dynamic environment. This free zone illustrates the possible maneuver margin of the aircraft on the whole flight trajectory. Displaying this zone on a viewing screen of the cockpit thereby allows the crew, and including the pilot(s), to carry out a very quick evaluation of the piloting complexity on the trajectory being considered.

The method according to the present invention has more specifically the following advantages:

-   -   it therefore allows to support the crew in making a decision on         board. The pilot's extrapolation ability does not necessarily         allows him to evaluate whether the flight trajectory being         followed is free of collision with a dynamic obstacle (for         example a stormy cell) moving in a tactical horizon. The present         invention analyzes the potential evolutions of the environment         and presents, by means of a simple display, the information         allowing to evaluate the validity of the trajectory; and     -   in addition to analyzing whether the trajectory goes through a         zone being considered as hazardous, the method according to this         invention provides a freedom zone (free zone) on the whole         trajectory, representing the maneuver margin of the aircraft.         Displaying this zone on a viewing screen allows the crew to         rapidly carry out an evaluation of the characteristics and of         the hazards along the trajectory being considered.

The present invention therefore provides a single display representing all the evolutions of the environment with respect to the flight trajectory in a given time window.

Within the context of present invention, it is possible to implement said collision trial, and more generally this invention, in a horizontal (side) plane or in a vertical plane. However, in a preferred embodiment, this invention is simultaneously implemented both in the horizontal and vertical planes so as to determine and provide a free zone being defined in the whole space around the flight trajectory being considered.

Furthermore, advantageously, if a part of the flight trajectory goes through any (stationary or mobile) obstacle of one of said first and second databases, this situation is emphasized on the display achieved at step C/, in particular by an absence of free zone and an overgloss of the part of the trajectory being impacted.

Moreover, advantageously:

-   -   at step A/, successive points are automatically determined, as         trials points, along the flight trajectory, being separated one         from the other, each time, by a constant distance; and/or     -   at step A/a), the passage time at the trial point being         considered is estimated as a function of the passage time         estimated at the previous trial point and of an estimated speed         of the aircraft.

For implementing the present invention, one or more first databases are used containing mobile (or dynamic) obstacles. In particular, advantageously, at step A/:

-   -   a first database is taken into consideration containing mobile         obstacles representing meteorological disturbance zones. In this         case, at step A/b), the position of each one of said mobile         obstacles is extrapolated at said passage time, taking into         consideration determining points defining the limits of         meteorological disturbance zones and of wind speed vectors         illustrating the shift of the wind at said determining points,         these determining points and these speed vectors being issued         from said first database; and/or     -   a first database is taken into consideration containing mobile         obstacles representing surrounding aircrafts. In this case, at         step A/b), the position of each one of said mobile obstacles is         extrapolated at said passage time, taking into consideration         information relative to the flight of said surrounding         aircrafts, including flight planes, being issued from said first         database. For implementing such an extrapolation, other         information can also be used, as set forth below.

Furthermore, advantageously, at step A/c):

-   -   a trial vector is used having a predetermined length; and/or     -   a collision trial is implemented for the extrapolated positions         of the mobile obstacles at two successive instants corresponding         to the extreme times of a time window being defined compared to         said passage time.

Moreover, advantageously, at step A/c), upon a collision trial:

-   -   if the trial vector does not meet any obstacle, the critical         point is located (and defined) at the end of said trial vector;         and     -   if the trial vector meets at least one obstacle, the critical         point is located (and defined) at the position of the obstacle         being the closest to the trial point being considered.

This invention further relates to a device for aiding the crew of an aircraft, in particular of a transport airplane, to evaluate any flight trajectory being intended to be followed by this aircraft in a constrained environment, that is in an environment able to contain stationary and mobile obstacles.

According to this invention, said device is remarkable in that it comprises:

-   -   at least one first database containing mobile obstacles,         relative at least to the environment of said aircraft, said         mobile obstacles representing more specifically meteorological         disturbance zones and/or surrounding aircrafts;     -   at least one second database containing stationary obstacles,         relative at least to the environment of said aircraft;     -   means for automatically determining a plurality of successive         points of said flight trajectory, referred to as trial points;     -   means for estimating the passage time of the aircraft at each         one of said trial points;     -   extrapolation means for extrapolating the positions of mobile         obstacles at said passage time, by means of said first database;     -   means for implementing a collision trial with the aim to check         whether a trial vector, being provided perpendicularly to a         shifting vector of the aircraft at said trial point, intercepts,         on the one hand mobile obstacles at extrapolated positions at         said passage time, and on the other hand stationary obstacles of         said second database, and for determining critical points on         opposite sides of the trial point being considered, as a         function of the result of said collision trial;     -   means for automatically presenting, on a viewing screen of the         aircraft, said flight trajectory, as well as, associated with         the latter, a free zone linking together said critical points         and allowing to aid to evaluate the flight trajectory.

The device according to this invention allows to represent the complexity of an evolutionary environment (a situation wherein the pilot's extrapolation ability is not satisfactory for representing the time dependent space freedom) by a simple display, the main information being the freedom zone (referred to as a free zone) being associated with the flight trajectory in a dynamic environment. Said device thereby allows to aid the crew of the aircraft in evaluating and validating their flight trajectories in a constrained environment.

The present invention further relates to an aircraft, in particular a transport airplane, provided with an aiding device such as mentioned hereinabove.

The FIGS. of the appended drawing will better explain how this invention can be implemented. In these FIGS., like reference numerals relate to like components.

FIG. 1 is a block diagram of a device according to this invention.

FIGS. 2 to 6 are diagrams for explaining the determination according to this invention of a free zone being associated with a flight trajectory of an aircraft.

FIGS. 7 and 8 are schematic diagrams illustrating displays according to the present invention in two different situations.

The device 1 according to this invention and schematically shown on FIG. 1, aims at aiding the crew of an aircraft (not shown), in particular of a transport airplane, to evaluate any flight trajectory TV being intended to be followed by this aircraft in a constrained environment. A constrained environment means an environment being able to contain objects or obstacles O1, O2, with which the aircraft should avoid getting into collision. These obstacles may be either stationary obstacles O1 such as mountains or hills or even mobile (or dynamic) obstacles O2 such as meteorological disturbance zones, including stormy zones or other aircrafts.

According to the invention, said device 1 being on board the aircraft comprises, as shown on

FIG. 1:

-   -   a set 2 of information sources for transmitting data, and         including the flight trajectory TV being considered;     -   at least one first database 3, 4 containing mobile obstacles O2         located in the environment of the flight trajectory TV, and         preferably a database 3 containing information on mobile         obstacles O2 representing meteorological disturbance zones and a         database 4 containing information on mobile obstacles O2         representing surrounding aircrafts;     -   at least one second database 5 containing stationary obstacles         O1 located in the environment of the flight trajectory TV;     -   one processing unit 6 being linked via links 7 to 10         respectively to said elements 2 to 5 and being formed so as to         determine, in particular, a free zone ZL allowing to aid         evaluating the flight trajectory TV, as set forth below; and     -   means 12 being linked via a link 13 to said processing unit 6         and being formed so as to automatically present, on a viewing         screen 14 of the cockpit of the aircraft, said flight trajectory         TV, as well as, associated to this flight trajectory TV, said         free zone ZL.

Moreover, according to the invention, said processing unit 6 comprises:

-   -   means 15 for automatically determining a plurality of successive         points of said flight trajectory TV, referred to as trial points         Pt;     -   means 16 for estimating the passage time of the aircraft at each         one of said trial points Pt;     -   extrapolation means 17 for extrapolating the positions of the         mobile obstacles O2 at said passage time, by means of the         databases 3 and 4;     -   means 18 for implementing a collision trial with the aim to         check whether a trial vector 22, being provided perpendicularly         to a shifting vector 20 of the aircraft at said trial point Pt,         intercepts, on the one hand mobile obstacles O2 at extrapolated         positions at said passage time, and on the other hand stationary         obstacles O1 of said second database 5, and for determining         critical points on opposite sides of the trial point Pt being         considered, depending on the result of said collision trial; and     -   means 19 for linking together the thus determined critical         points Pc so as to form the limits (or outline) 21 of said free         zone ZL.

Thus, the device 1 according to this invention provides a display (FIGS. 7 and 8) emphasizing a zone ZL being free from any obstacle around a flight trajectory TV being defined in a dynamic environment. This free zone ZL illustrates the possible maneuver margin of the aircraft on the whole flight trajectory TV. Displaying this zone ZL on a viewing screen 14 of the cockpit thereby allows the crew, including the pilot(s) to carry out a very quick evaluation of the piloting complexity on the trajectory being considered.

Within the context of the present invention, the above mentioned operations can be implemented in a horizontal plane or in a vertical place. However, in a preferred embodiment, this invention is simultaneously implemented both in the horizontal and vertical planes so as to determine and provide a free zone ZL being defined in the whole space around the flight trajectory TV being considered.

As set forth below, the processing unit 6 operates in an iterative way. It provides a number of distinct positions (trial points Pt) on the trajectory TV as a function of a predefined incrementation. For each one of these positions, it provides an estimation of the passage time, based on the predictions achieved by a flight management system integral for example, with the set 2. It then generates a representation of the environment at the estimated time, such a representation being used as a reference for measuring the critical distances compared to the obstacles O1, O2. Displaying all the critical points Pc for each one of the positions (trial points Pt) on the trajectory TV allows the representation, in one single display, of potential evolutions of the environment with respect to the trajectory written in a time window.

A detailed description of the characteristics of the present invention is carried out hereinafter for the side (horizontal) plane, the implementation being similar for the vertical plane.

The processing unit 6 thus relies on reference information issued from the following information sources:

-   -   the database 5 of the ground, representing stationary,         constraints;     -   the meteorological database 3. This information could be issued         from the on-board meteorological monitoring or be received via a         usual link of data transmission;     -   the database 4 relative to surrounding aircrafts, containing the         flight planes and the predictions of the aircrafts identified in         a given perimeter; and     -   the set 2 supplying, more particularly, the current flight         trajectory TV, followed by the aircraft (on-board which the         device 1 is arranged).

Said device 1 thus relies on two types of separately processed databases:

-   -   a stationary database 5, representing obstacles O1 the position         of which does not progress during the flight; and     -   dynamic databases 3 and 4, representing all the moving obstacles         O2 that the operator wishes to take into consideration it his         evaluation.

The stationary obstacles base 5 contains discretizations of obstacles O1. The representation is a polygonal projection on the ground, associated with a limit height.

The dynamic bases 3, 4 integrate, as far as they are concerned, additional information regarding the evolution of the zones.

For stormy zones Z1, the information is produced by an analysis of the recent evolution of the zones (analysis of the meteorological monitoring or of data transmitted by a data transmission link for example). This analysis produces, for each building point A1 to A6 (referred to as a determining point) of the polygonal surface S1 (forming the mobile object or obstacle O2), a mean shifting vector V1 to V6 being measured, as shown on FIG. 2. On this FIG. 2, a wind speed vector V0 is also emphasized.

As far as aircrafts are concerned being in a potential conflict with the trajectory TV being considered (database 4), they are each time associated with a flight plane, a speed profile and a hazard zone width around the aircraft.

Furthermore, said means 15 determine automatically, as trial points Pt, successive points along the flight trajectory TV, being separated one from the other, each time, by a constant distance D, as shown on FIG. 3. This distance D could be predetermined, or even be selected and entered in the device 1 by an operator using appropriate means integral with the set 2.

Moreover, the means 16 estimate the passage time at each trial point Pt being considered. The prediction occurs on an interpolation between the trial points Pt provided by the flight management system. The time generated is produced with respect to a current time t0 at the current position P0 of the aircraft. The next trial point P1 is thus located at a distance D from P0 and is identified by a passage time t0+x.

Furthermore, said extrapolation means 17 extrapolate the positions of each one of the mobile obstacles O2 (aircrafts on a flight plane, stormy cells on analyzed vectors, etc.). The extrapolation occurs on a tolerance window aiming at overcoming the inaccuracies at the level of the predictions. This tolerance window could be predetermined, or even be selected and entered in the device 1 by an operator using appropriate means being integral with the set 2.

For each one of the trial points Pt, said extrapolation means 17 analyze the predicted passage time being associated therewith. Then, they carry out a position extrapolation based on the shifting vectors

V1 to V6 stored in the associated database 3, 4. Each one of the mobile obstacles O2 is thus shifted for each one of the trial points Pt.

As previously set forth, for implementing the present invention, one or more databases can be used containing mobile (or dynamic) obstacles O2. In particular,

-   -   for the database 3 containing mobile obstacles O2 representing         meteorological disturbance zones, said extrapolation means 17         extrapolate the position of each one of said mobile obstacles O2         at said passage time, taking into consideration determining         points A1 to A6 defining the limits of the meteorological         disturbance zones and of the vectors V1 to V6 illustrating the         shift of the wind at said determining points A1 to A6, such         determining points A1 to A6 and such speed vectors V1 to V6         being contained in said database 3; and/or     -   for the database 4 containing mobile obstacles O2 representing         surrounding aircrafts, said extrapolation means 17 extrapolate         the position of each one of said mobile obstacles O2 at said         passage time, taking into consideration information relative to         the flight of said surrounding aircrafts, including the flight         planes, being issued from said database 4. For implementing this         extrapolation, other information can also be used, for example         estimations of the trajectories of said surrounding aircrafts as         a function, including, of their current course and their current         speed.

Furthermore, for implementing collision trials, the means 18 use a collision trial vector 22 having a length being predetermined, for example 6 nautical miles, or being selected by the pilot using appropriate means integral, for example, with the set 2. For each one of the trial points Pt, they plot collision trial vectors 22 perpendicularly to the shifting vector 20 of the aircraft, on opposite sides of the trial point Pt being considered. Moreover, they implement a collision trial for the extrapolated positions of the mobile obstacles O2 at two successive instants TiA and TiB corresponding to the extreme times (Ti−F, Ti+F) of a time window FT being defined compared to said passage time Ti. As shown on the chronological plot shown on FIG. 4, the definition of this window FT, taking into consideration a duration F around the passage time Ti, allows to identify three determining (successive according to the time t) positions, respectively at said times Ti−F, Ti and

Ti+F. The duration F represents a multiple of a pitch P. In a particular embodiment, this time window FT could be nil.

Thus, as an illustration:

-   -   in the example of FIG. 5, the collision trial being carried out         for a mobile obstacle O2 at a trial point Pt located at a point         P3 (with a passage time T3), is implemented compared to two         extrapolated positions 23 and 24 of this mobile obstacle O2         respectively at times T3−F and T3+F; and     -   in the example of FIG. 6, the collision trial being carried out         for a mobile obstacle O2 at a trial point Pt located at a point         P4 (with a passage time T4), is implemented compared to two         extrapolated positions 25 and 26 of this mobile obstacle O2         respectively at times T4−F and T4+F.

Moreover, during such a collision trial:

-   -   if the trial vector 22 meets at least one obstacle 23, 24, the         critical point Pc is defined at the position of the obstacle 23         being the closest to the trial point Pt being considered, as         shown on the example of FIG. 5; and     -   if the trial vector 22 does not meet any obstacle, the critical         point Pc is defined at the end of said trial vector 22, as shown         on the example of FIG. 6.

The trial (or interception) vector 22 is constrained by a limit length imposed, for example, by an operator. This length is associated with a maximum coverage margin. If the trial vector 22 does not meet any obstacles within this margin, the critical point Pc is thus defined as a function of the limit size. On the other hand, if a point is located within a hazardous cell, this point is identified as critical. A critical point Pc is specially processed upon the display for emphasizing the hazard associated with the trajectory TV.

The plot according to the critical points Pc, on opposite sides of the reference trajectory TV, defines the limits 21 of the dynamic free zone ZL, as shown on FIGS. 7 and 8.

On these FIGS. 7 and 8:

-   -   the plots 21 in a thick solid line thus define, on opposite         sides of the flight trajectory TV, the free zone ZL;     -   the plot TV in a thin solid line defines the flight trajectory         being considered;     -   the plots 28 in mixed lines define the stationary obstacles O1;         and     -   the plots 29 with dashes define the mobile obstacles O1, in         particular stormy zones that are going to progress.

Furthermore, if a part T2 of the flight trajectory TV goes through an (stationary or mobile) obstacle, this situation is emphasized on the display, in particular by a lack of free zone (plot 21) and by an overgloss of the impacted part of trajectory T2 (illustrated by a thick line on FIG. 8). On FIG. 8, going through a mobile obstacle 29 (the shifting vector 30 of which has been represented for exemplifying its shift) is thus emphasized by the above-mentioned characteristics.

The device 1 according to the present invention thus has, more specifically the following advantages:

-   -   it allows to support the crew in making a decision on board. The         pilot's extrapolation ability does not necessarily enable him to         evaluate whether the flight trajectory TV being followed is free         of collision with a dynamic obstacle O2 (for example a stormy         cell) moving in a tactical horizon. The present invention         analyzes the potential evolutions of the environment and         presents, by means of a simple display, the information allowing         to evaluate the validity of the trajectory TV; and     -   in addition to analyzing whether the trajectory goes through a         zone being considered as hazardous, the method 1 according to         this invention provides a freedom zone (free zone ZL) on the         whole trajectory, representing the maneuver margin of the         aircraft. Displaying this zone ZL on the viewing screen 14         allows the crew to rapidly carry out an evaluation of the         characteristics and of the piloting hazards along the trajectory         TV.

The present invention therefore provides a single display representing all the evolutions of the environment with respect to the flight trajectory TV in a given time window. 

1. A method for aiding to evaluate a flight trajectory (TV) intended to be followed by an aircraft in a constrained environment: characterized in that: A/ at least one first database (3, 4) containing mobile obstacles (O2) and at least one second database (5) containing stationary obstacles (O1) relative at least to the environment of the aircraft, are taken into consideration, a plurality of successive points of said flight trajectory, referred to as trial points (Pt) are automatically determined, and the following operations are automatically implemented and this individually for each one of said successive trial points (Pt) of said flight trajectory (TV): a) the passage time of the aircraft is estimated at the trial point (Pt) being considered; b) the positions of the mobile obstacles (O2) at said passage time are extrapolated by means of said first database (3, 4); and c) at least one collision trial is implemented for checking whether a trial vector (22), being provided perpendicularly to a shifting vector (20) of the aircraft at said trial point (Pt), intercepts, on the one hand, mobile obstacles (O2) at extrapolated positions at said passage time, and on the other hand, stationary obstacles (O1) of said second database (5), and critical points (Pc) are determined on opposite sides of the trial point (Pt) being considered, depending on the result of said collision trial; B/ the thus determined critical points (Pc) are automatically linked together so as to form a zone, referred to as a free zone (ZL), around said flight trajectory (TV); and C/ said flight trajectory (TV) is automatically shown on a viewing screen (14) of the aircraft, as well as, associated with the latter, said free zone (ZL) allowing to aid to evaluate the flight trajectory (TV).
 2. The method according to claim 1, characterized in that at step A/, as trial points (Pt), successive points along the flight trajectory (TV) are automatically determined, being separated from each other, each time, by a constant distance (D).
 3. The method according to claim 1, characterized in that at step A/a), the passage time at the trial point being considered (Pt) is estimated as a function of the passage time estimated at the previous trial point and of an estimated speed of the aircraft.
 4. The method according to claim 1, characterized in that at step A/, a first database (3) is taken into consideration containing mobile obstacles (O2) representing meteorological disturbance zones, and in that at step A/b), each one of said mobile obstacles (O2) at said passage time is extrapolated, taking into consideration determining points (A1 to A6) defining the limits of the meteorological disturbance zones and of the wind speed vectors (V1 to V6) illustrating the wind shift at said determining points (A1 to A6), these determining points (A1 to A6) and these speed vectors (V1 to V6) being issued from said first database (3).
 5. The method according to claim 1, characterized in that at step A/, a first database (4) is taken into consideration containing mobile obstacles (O2) representing surrounding aircrafts, and in that at step A/b), the position of each one of said mobile obstacles (O2) is extrapolated at said passage time, taking into consideration information relative to the flight of said surrounding aircrafts, being issued from said first database (4).
 6. The method according to claim 1, characterized in that at step A/c), a collision trial is implemented for the extrapolated positions of the mobile obstacles, at two successive times corresponding to extreme times of a time window (TF) being defined compared to said passage time.
 7. The method according to claim 1, characterized in that at step A/c), said trial vector (22) has a predetermined length.
 8. The method according to claim 1, characterized in that at step A/c), upon a collision trial: if the trial vector (22) does not meet any obstacle, the critical point (Pc) is located at the end of said trial vector (22); and if the trial vector (22) meets at least one obstacle (23, 24), the critical point (Pc) is located at the position of the obstacle (23) being the closest to the trial point (P3) being considered.
 9. The method according to claim 1, characterized in that, if a part (T2) of the flight trajectory (TV) goes through any obstacle (29) of one of said first and second databases (3, 4, 5), this situation is emphasized on the display achieved at step C1.
 10. The method according to claim 1, characterized in that at least said collision trial is implemented in a horizontal plane.
 11. The method according to claim 1, characterized in that at least said collision trial is implemented in a vertical plane.
 12. A device for aiding to evaluate a flight trajectory (TV) intended to be followed by an aircraft in a constrained environment: characterized in that it comprises: at least one first database (3, 4) containing mobile obstacles (O2), relative at least to the environment of said aircraft; at least one second database (5) containing stationary obstacles (O1), relative at least to the environment of said aircraft; means (15) for automatically determining a plurality of successive points of said flight trajectory, referred to as trial points (Pt); means (16) for estimating the passage time of the aircraft at each one of said trial points (Pt); extrapolation means (17) for extrapolating the positions of the mobile obstacles (O2) at said passage time, by means of said first database (3, 4); means (18, 19) for implementing a collision trial with the aim to check whether a trial vector (22), being provided perpendicularly to a shifting vector (20) of the aircraft at said trial point (Pt), intercepts, on the one hand, mobile obstacles (O2) at extrapolated positions at said passage time, and on the other hand, stationary obstacles (O1) of said second database (5), and for determining critical points (Pc) on opposite sides of the trial point (Pt) being considered, as a function of the result of said collision trial; and means (12) for automatically showing, on a viewing screen (14) of the aircraft, said flight trajectory (TV), as well as, associated with the latter, a free zone (ZL) linking together said critical points (Pc) and allowing to aid to evaluate the flight trajectory (TV).
 13. The device according to claim 12, characterized in that it comprises a first database (3) containing mobile obstacles (O2) representing meteorological disturbance zones, and in that said extrapolation means (17) extrapolate the position of each one of said mobile obstacles (O2) at said passage time taking into consideration determining points (A1 to A6) defining the limits of the meteorological disturbance zones and of the wind speed vectors (V1 to V6) illustrating the wind shift at said determining points (A1 to A6), these determining points (A1 to A6) and these speed vectors (V1 to V6) being issued from said first database (3).
 14. The device according to claim 12, characterized in that it comprises a first database (4) containing mobile obstacles (O2) representing surrounding aircrafts, and in that said extrapolation means (17) extrapolate the position of each one of said mobile obstacles (O2) at said passage time, taking into consideration information relative to the flight of said surrounding aircrafts, being issued from said first database (4).
 15. An aircraft, characterized in that it comprises a device (1) such as specified in claim
 12. 